We finally managed to make the customers of the quality of the vehicle.A. to convinceB. c

问题补充：

We finally managed to make the customers of the quality of the vehicle.

A. to convince

B. convincing

C. convince

D. convinced

答案：

A. to convince

B. convincing

C. convince

(答案→)D. convinced

解析：convince sb. of sth. 使某人确信某事，句中的customers作make的宾语，后面却宾补，而convince与the customers之间是被动关系，因此选D。